Free transfer machine with independent motorized carriages

ABSTRACT

The present invention relates to a free transfer machine equipped with independent motorized carriages. Each carriage comprises a variable speed motor, a rechargeable battery connected to contact blocks, and an individual travelling control system comprising a motor supply and control circuit which is controlled by a switch actuated by a front bumper and by a contactor mounted in series with the switch and carried by the lower face of the carriage in such a way as to be actuated by the rectractable stop members. The circuit is also under the control of environmental sensors. The carriages travel on trackways which include work stations, reed-contacts connected to an electric charge device and designed to operate with the contact blocks. The transfer machines are suitable for production and assembly lines.

FIELD OF THE INVENTION

The present invention relates to the transport of various types of loadsor workpieces between work or intervention stations which may beoperating stations, control stations, assembling stations, assemblingstations, testing stations, etc.

BACKGROUND OF THE INVENTION

The need to resort to an automatic transfer between a succession of workstations, has been felt for a long time now, in order to rationalize amanufacturing, assembling, mounting or treating process and to reduce,if not eliminate completely, all human intervention at each operationalstep in such a process.

To reach this object, the prior art has proposed a number of solutionswhich can be classified in two families corresponding, respectively, totransfer machines with bound carriages and to transfer machines withfree carriages.

In the first family, the machines define a trackway, set up in relationwith the different work stations. Such a trackway is used for moving andguiding carriages which are interconnected in the manner of an endlesschain or conveyor, driven by any suitable drive member.

Such a solution may present certain advantages in special applicationsin which the mass of workpieces or of loads to be transferred is quitesmall. In other cases, such a solution present starting and stoppingproblems, on account of the inertia represented by all the transfercarriages organized in the form of an endless unitary chain.

One related problem resides in the difficulty of using suitable indexingmeans which are, nonetheless, necessary in front of each work station,so that the elementary operations so that any elementary operationrelative to every stopping phase, in relation to the supportedworkpieces or loads, can be performed with as much accuracy as possible.

Conceivably, this requirement is not very compatible with theorganization of a large number of transfer carriages into an endlesschain, in which the successive interconnections of the carriages, whichare necessarily articulated, introduce a tolerance factor which isdifficult to control.

The transfers, known as bound transfers, are not either a particularlyadaptable technical solution since there is no possibility with such astructure, of organizing by-pass tracks or stand-by sectors, and alsosince the moving cycle must, necessarily, conform with the longestindividual operation time of all the work stations.

Such transfers therefore have a limited output and offer but littleadaptability when an intervention is necessary in the course of thegeneral process, or when it becomes imperative to use such transfers forcarrying out operations for which it was not initially designed.

The transfer machines of the second family have been designed toovercome the aforesaid necessities. Such machines comprise a trackwaydefining guiding and supporting rails for free and independent carriageswhich are moved from one work station to the other, via drive membersincorporated to the trackway.

It is unquestionable that such an organization has represented apositive evolution with respect to the transfer machines of the otherfamily. Yet, a number of disadvantages are also found with thesetransfer machines with free carriages.

The carriages, which are placed on the trackway, are entirely controlledby that trackway and are dependent on the driving means incorporated insaid trackway. This implies that the speed of such carriages is limitedbecause there is no damping of the acceleration and decelerationphenomena which, however, should be limited in order to reduce shocks,particularly when the transfer machine has stopped, either in front of awork station, or because the carriages are in direct abutting contact.

The means of starting off the different carriages must, necessarily, beprovided throughout the length of the trackway, this requiring a largenumber of drive members, which increases the risks of loss ofsynchronization, of wear, of failure, of noise, of bulkiness and ofsafety.

Although such machines can be produced in modular form, theynevertheless offer little adaptability, because of the necessity ofalways using the same constituting elements comprising a source ofpower, transmission members, as well as guiding members which, ingeneral, cannot really be arranged in any other way but the linear way.The plan configurations which can be given to the trackway are, as aresult, limited or else they require the use of direction changingsystems which are even more complex and which, in general, have beenfound to be at the origin of delicate adjustments and of breakdowns,often difficult to control.

Because the elementary modules imply making use of all the constitutingmembers, any modification will involve a lengthy stoppage time as wellas delicate and costly operations, particularly when a part of thetrackway between two work stations have to be modified.

And because the drive member and the transmission elements arenecessarily incorporated, the overall thickness of every modular elementis great and may, in some cases, raise problems of implantation forhand-operated work stations, for which a steady efficiency is always thetarget.

Though the existence of free and independent transfer carriages makes itpossible, when defining a general work cycle, to do away with thelongest operation time of one of the work stations, the maximum movingspeed, between stations, is, on the contrary, limited to the capacity ofthe transmission members provided in the trackway. In order tocounterbalance said limited speed, it is generally admitted to have alarge number of free carriages travelling on the trackway. In additionto the resultingly increased overall dimensions of the trackway, theexcess number of carriages unavoidably causes a localized accumulation,for example against one carriage being stopped in working service infront of a work station. In such a case, the number of carriages blockedhorizontally on the trackway, increases very considerably the frictionwith the transmission members and strains noticeably the motor whichdrives them continuously. In addition, such accumulation occurs againstthe carriage which is stopped against the retractable stop member of awork station. Said stop member then undergoes a great thrust, resultingfrom an accumulation of the elementary frictions between thetransmission members and the stacked carriages. Such thrust is often thecause of a deterioration of the structure or of the stopping position ofthe retractable stop member.

On the whole, therefore, the transfer machines equipped with freecarriages, although they bring advantages over the machines of the otherfamily, are not yet fully satisfactory, and are currently found to raisecertain unsolvable problems of incorporation in fully automaticproduction lines using robotized work stations which, by their verystructure, experience appreciably different operating times within thesame production line.

In order to reduce the number of the aforementioned disadvantages, theprior art has concentrated on developing the transfer machines of thesecond family. One particular French patent application FR-A-2 585 008(85-11048) can be cited to this effect. This application describes anautomatic transfer machine equipped with transfer means constituted byrails and autonomous carriages or pallets, provided with their owndriving means. The autonomy-inducing means consist in an electric motorwhich is carried by the pallet and supplied by shoes operationallycoupled with collectors carried by the rails.

Such a machine is also equipped with a centralized system forcontrolling the progress of the pallets by using a central unit,programmed by local passage sensors, to remote-control the supply ornon-supply of electric power to the collectors.

Although this particular construction is an improvement over theprevious solutions, it remains nonetheless unsatisfactory for thefollowing reasons.

The real object is to make the machine adaptable in operation, so thatit will allow the performance of industrial processes liable to certainvariations, the aim there being to enable the use of the transfermachine for carrying out different operations which do not all takeplace automatically in succession. It would then be possible with such amachine to carry out different production programmes, for the samearticle or for different articles, and thus to be able to meet thedemand.

In order to reach this object, it is important to find a solution to twokinds of problems.

The first one is that of a reliable self-supply of driving power, andthe solution proposed by Application FR-A-2 585 008 does not fulfill theobject. It is indeed a known fact that when shoes are moved oncollectors, especially with a low voltage current, this causes a"charring" effect which instantly changes the conditions of transmissionof the electric power. As a result, no reliable-in-time displacement ofa pallet equipped as aforementioned can be guaranteed.

The second problem is that of the control of the displacement of all thepallets or carriages transporting loads from one work station toanother, where operations of different durations are conducted.Application FR-A-2 585 008 has not, by centralizing the control of theoverall displacement, procured a smooth running, as in fact this isfrozen by the programme of the central unit which merely takes intoaccount the preprogrammed passage detections to authorize theperformance of an operating sequence.

There is therefore an obvious need for a transfer machine, of the typewith free carriages, which will have none of the aforementioneddisadvantages, but which, on the contrary, will show an ability to adaptautomatically the time of transfer between two work stations, whateverthe distance separating these stations and the operating time requiredby each one.

SUMMARY OF THE INVENTION

It is precisely the object of the present invention to solve theabove-expressed problems by proposing a new free transfer machine withmotor-driven independent carriages.

The object of the invention is therefore to propose a new transfermachine composed of a support and guiding structure of particularlysimple design, with free and self-motorized carriages, capable ofstoring a reserve of power, which is partly reconstituted if the needarises, during a stop at a work station. The chains according to theinvention have the added capacity to adapt automatically their movingspeed as a function of the distance to be covered and of the conditionsfor stopping at a work station, so as to reduce to a minimum the actualtransfer time, independently of the configuration of the trackway and ofthe operating times required at each station, by using individualtravelling control means.

A further object of the invention is to propose means for organizing atrackway which can comprise rapidly and efficiently implanted changes ofdirection, without the need for a particularly complex structure. Thisoffers the possibility, never reached until now by the prior art, ofpermitting instant and ready modification of the implantation andconfiguration of a trackway as a function of an overall operationprocess to be performed.

Another object of the invention is to propose a new transfer machinehaving a trackway of the endless type, the configuration of which can bereadily adapted as a function of multiple operations requirements.

Another object of the invention is to propose a new free transfermachine which can have a loading and running structure of smallthickness, which will meet all the requirement of ergonomics, which iswithout any drive members moved in permanent and continuous manner andtherefore which offers maximum security for the operating personnel.

Yet another object of the invention is to propose new means forproducing a transfer machine of which the trackway can be set upinstantly, practically and reliably, between work stations which may besituated at different levels.

The aforesaid objects are reached according to the invention with a freetransfer machine of the type comprising a trackway set up in relation towork stations which are each provided with a retractable stop member andwith independent travelling carriages which are carried, guided anddriven along the trackway and which are designed to transfer the loadthat they support, from one work station to another, each carriage beingequipped with a set of driving wheels actuated by an on-board electricdrive member energized from an equally on-board battery, said freetransfer machine being characterized in that:

each carriage comprises:

a variable speed motor,

a rechargeable battery connected to contact blocks,

and an individual travelling control system comprising a motor supplyand control circuit which is controlled by a switch actuated by a frontbumper and by a contactor mounted in series with said switch and carriedby the lower face of the carriage in such a way as to be actuated by theretractable stop members, said circuit being also placed under thecontrol of environment sensors,

the trackway comprises, in relation with each work station,reed-contacts connected to an electric charge device and designed tocooperate with the contact blocks.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood on reading the followingdescription with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatical plan view of a transfer machine.

FIG. 2 is a cross-section, on an enlarged scale, along line II--II ofFIG. 1.

FIG. 3 is an elevational section, partly broken out, taken along lineIII--III of FIG. 1.

FIG. 4 is a partly sectional view from below, taken along line IV--IV ofFIG. 3.

FIGS. 5 and 6 are cross-sections taken, respectively, along lines V--Vand VI--VI of FIG. 3.

FIGS. 7 and 8 are cross-sections taken, respectively, along linesVII--VII and VIII--VIII of FIG. 4.

FIGS. 9 to 11 are partial sections showing, on an enlarged scale,certain embodiment details.

FIG. 12 is a partial cross-section taken along line XII--XII of FIG. 2.

FIG. 13 is a diagram illustrating a servo-control system for controllingthe travelling speed of the carriages of the transfer machine accordingto the invention.

FIG. 14 is a block diagram illustrating the automatic working phases ofthe object of the invention.

FIG. 15 is an elevational section taken along line XV--XV of FIG. 2.

FIG. 16 is a diagrammatical cross-section showing variants of embodimentof certain members.

FIG. 17 is a bottom view, similar to FIG. 4, illustrating anotherembodiment of the object of the invention.

FIG. 18 is a partial elevational view of one member of the machineaccording to the embodiment shown in FIG. 17.

FIG. 19 is a bottom view showing the cooperation between the elementsaccording to FIGS. 17 and 18.

FIG. 20 is an elevational section taken along line XX--XX of FIG. 19.

FIG. 21 is a plan view illustrating one possibility of implantation ofthe machine offered by the means shown in FIGS. 17 and 18.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Referring now to the drawings, FIG. 1 diagrammatically illustrates atransfer machine according to the invention, composed of a trackway Ipermitting the transport of workpieces or loads of various types betweenwork stations, of which two only P₁ and P₂ are diagrammatically shown.

The trackway I extends between a table T₁ for loading the workpieces tobe transported and a table T₂ for unloading said workpieces. Saidtrackway I is essentially constituted (FIG. 2) by two parallel rails R₁and R₂ mounted on a carrying structure II. Rails R₁ and R₂, constitutedfor example by tubular sections, provide by way of their internal faces,running surfaces 1 and lateral guiding surfaces 2 of horizontal andvertical cross-sections respectively.

Surfaces 1 and 2 are provided for supporting and guiding a motor-drivencarriage 5 which comprises, as illustrated in FIGS. 3 to 8, a plate 6normally equipped on its upper face 6a, with means for removablypositioning and centering workpieces or loads. Said means, which are theconventional ones used with transfer machines, have not been shown inthe drawings because they are essentially dependent on the selectedapplication, and they are known of anyone skilled in the art.

The plate 6, which is preferably bordered on its periphery by a skirt orfairing 7, is provided on its lower face 6b with runners 8 projectingslightly with respect to longitudinal faces 6c for cooperating with theguiding surfaces 2. The face 6b also supports rolling members 9 designedto cooperate with the surfaces 1. Said rolling members 9 are preferablyconstituted by wheels with separate adhering tires and are so arrangedas to form a rear train 10 and a front train 11. The rear train 10 iscomposed of two extreme wheels 9 mounted on a shaft 12 fitted viarollers 13 in bearings 14 of the plate 6. Shaft 12 is powered by a motorunit 15 and preferably by a geared motor unit. Unit 15 comprises avariable speed motor 16 mounted on the lower face 6b so as to extend inparallel to shaft 12. Unit 15 further comprises a reduction gear 17placed between the output shaft 18 of the motor 16 and the shaft 12.Reduction gear 17 is for example of the three-step type, usingpreferably for each step, a synchronous belt drive. The synchronous beltdrive method is preferably selected to allow the transmission of a hightorque, at high speed and with little noise.

FIG. 9 clearly shows that the reduction gear 17 is so designed that itsfirst reduction step is constituted by an output gear 19 mounted on theshaft 18 and by a driven gear 20 mounted on a countershaft 21. Accordingto a preferred embodiment, the countershaft 21 is of tubular type and iscarried via rollers 22, concentrically to and on driving shaft 12.Countershaft 21 carries a driving gear 23 for the second reduction stepwhich is constituted by said gear 23 and by a gear 24 mounted on acountershaft 25 parallel to shaft 12 and co-axial, for example, tooutput shaft 18. Countershaft 25 is carried by a double bearing 14adefined by the corresponding bearing 14. Countershaft 25 carries a gear26 which constitutes the third reduction step and cooperates with anadditional gear 27, wedged angularly and axially on driving shaft 12 fordriving said shaft in self-motivated rotation.

In the illustrated embodiment, the driving shaft 12 of the train 10 isconnected, via preferably a belt transmission 28, to the train 11 whichis composed of two wheels 9 mounted on a shaft 29, which shaft ismounted, via rollers 30, in bearings 31 of the plate 6, so as to extendin parallel to shaft 12.

The motor-driven rear train 10 is, preferably, associated to anelectro-mechanical braking member 32, as more particularly illustratedin FIGS. 10 and 11. Braking member 32 comprises an annular magnetic coil33 mounted on the bearing 14 so as to be situated concentrically toshaft 12 close to a wheel 9. Annular coil 33 is provided, on its faceopposite the annular face 9a of the wheel 9, with an annular frictiondisk 34, preferably removably mounted on the coil 33. Said friction disk34 is oriented in facing relationship to face 9a supporting an annulardisk 35 in magnetic material, mounted via elastically deformable strips36 in such a way as to be angularly fixed with possibility of lateralshifting with respect to face 9a. The electro-magnetic coil is mountedin such a way as to leave a small gap between the friction disk 34 andthe disk 35 in its stable resting position against face 9a.

The lower face 6b of the plate 6 is provided with two stiffening members37, starting from its front face 6e, and which are formed by or built onsaid plate, said members being equipped with sole plates 37a. Stiffeningmembers 37 extend in parallel one to the other and on either side of alongitudinal median plane of symmetry x-x', from the front face 6e toclose to shaft 12. Consequently, said stiffening members 37 aretraversed by the shaft 29 of the front train 11 for which they defineco-axial passageways 38.

Stiffening members 37 define, from the lower face 6b, two lateralcompartments 39 which are occupied, between trains 10 and 11, by tworechargeable accumulator batteries 40 constituting an on-board source ofelectrical power supplying the motor. Batteries 40 are electricallyconnected to at least two contact blocks 41 provided on the lower face6b and extending toward the plane traversing the running surfaces 1.

Said contact blocks 41 are preferably provided on the plate close to therear face 6d and on the side opposite reduction gear 17. Said blocks 41are designed, as illustrated in FIGS. 2 and 12, to cooperate with reedcontacts 42 carried by an insulating block 43 mounted close to the railR₂. The reed contacts 42 are connected to an electrical chargetransformer in order to recharge the batteries 40 every time thecarriage 5 is stopped in front of a station P. In this case, the reedcontacts 42 form part of the equipment of a station P.

The stiffening members 37 define together a central compartment 44 whichis preferably reserved for the mounting and protection of an electronicservo-control circuit 45, controlling from the source of power 40, thehigh speed or slow speed supply of motor 16, as well as thede-energizing of the electro-mechanical brake 32. To this effect, theservo-control circuit 45 comprises, first of all, an inductive sensor 46carried by the plate 6 so as to face the general plane of the runningsurfaces 1. Said inductive sensor is designed to detect the presence ofbars 47 carried either by the running surfaces, or preferably, by aclosing plate 48 carried by the structure II (FIG. 2). Each bar 47represents an item of information which pre-materializes the existenceor position on or close to the trackway I of a singularity because ofwhich the carriage 5 has to adopt a slow travelling speed. In theillustrated example, the trackway 1 of the transfer machine comprises abar 47 situated upstream of each station P.

The circuit 45 also comprises a telemetric presence finder 53, connectedin parallel with the sensor 46 and placed in the central compartment 44so as to be level with the front face 6e. Said telemetric finder 53 maybe of any suitable type for detecting the existence or presence of anobstacle, such as a carriage 5 occupying the trackway I in downstreamdirection.

The servo-control circuit 45 further comprises a sensor 56 for measuringthe travelling speed of the carriage along the trackway I. Such a sensorcan be constituted by a tacho-generator or by an encoder coupled to theelectric motor 16.

The working principle of the servo-control circuit 45 consists incontrolling the high speed supply of the motor 16, when no informationis supplied either by sensor 46 or by telemetric finder 53. On thecontrary, as soon as the sensor 46 or the finder 53 sends a presencesignal, the servo-control circuit 45 is required to control the power tothe motor in such a way as to impose a slowing down from the maximumspeed V_(max) to the minimum speed V_(min) of said motor.

FIG. 13 shows a working diagram corresponding to the servo-controlcircuit 45. Circuit 45 is designed in such a way as to generate, uponthe supply, at a time T_(O), by the sensor 46 or by the finder 53, of apresence signal, a signal CF representing an acceptable braking curve tobring the speed of the loaded carriage, from the value V_(max) to thevalue V_(min). Signal CF is preferably a linear curve.

Circuit 45 is designed to take into account a video signal CV of thevariation of the speed curve of carriage 5. Said signal CV is an analogsignal supplied by the tacho-generator.

Circuit 45 is designed to compare the signal CV with the signal CF and,if the value of signal CV exceeds signal CF, to stop the supply to themotor 16 and the energizing of the brake 32. The action of circuit 45 istherefore dependent on the speed curve of carriage 5, in order to brakethe speed of the latter just at the right time and to allow the highestpossible travelling speed for the longest possible time.

Circuit 45 is also designed to restore the low speed supply to the motor16 once the predetermined minimum speed of the carriage is reached bybraking.

In order to perform the aforesaid functions, the circuit 45 may, asillustrted in FIG. 14, include a two-stage comparator 60 comprising afirst stage 61 receiving in input analog signal CV representing thespeed curve and supplied by tacho-generator 56. Said stage 61 alsoreceives analog signal CF representing the braking curve CF supplied byan electronic computing module belonging the circuit 45. The role ofthecomparing stage is, first to stop the supply to the motor 16, andsecond, to energize the brake 32.

Comparator 60 comprises a second stage 63 receiving, first the signal CFsupplied by module 62, and then a signal C_(min) supplied by a module 64and corresponding to a low speed control set value. The output ofcomparator 63 is connected to the supply of electric motor 16 in orderto control said supply inat low speed and to the coil of brake 32 inorder de-energize it.

The servo-control circuit 45 confers to the carriage 5 individualautonomous means of controlling its travelling speed on the trackway I.Indeed, when no information is issued by the sensor 46 and/or by thefinder 53, the motor 16 is supplied for high speed and draws its powerfrom the source 40. The carriage is then driven at maximum speed on thetrackway I between two successive work stations, such as from P₁ to P₂.

When, for example, the telemetric detection cell 53 detects the presenceof an obstacle on the trackway I, such as for example the presence ofthe preceding carriage, the circuit 51 works out the most adequatemoment to trigger the slowing down phase, in order to bring the carriageto the minimum travelling speed near to the obstacle. The role ofcircuit 45 is therefore to determine the optimal moment for triggeringthe slowing down phase so as to retain a maximum travelling speed overthe longest possible path length, this in order to reduce to a minimumthe times when the carriage must travel at reduced speed.

Once a detection signal has been issued by the finder 53, the circuit 45generates the video signal CF of the theoretical slowing down curvewhich should be adopted between maximum speed V_(max) and minimum speedV_(min) of the carriage. Simultaneously, the control circuit 45 recordsanalog signal CV issued by the tacho-generator 56 and representing theimage of the actual travelling speed of the carriage. When this signalexceeds the value of the theoretical slowing down curve, theservo-control circuit 45 cuts off the supply to electric motor 16 andtriggers off the brake 32. Both actions therefore occur with a variabledelay with respect to the origin T_(O) of the detection signal, suchdelay being essentially dependent on the speed acquired by the carriageat the time of emission of the obstacle detection signal.

The speed of the carriage is slowed down by the brake 32 until such timeas the theoretical braking curve CF, or even a real speed detectionwhich could have been supplied by the tacho-generator 56, generates asignal corresponding to the set signal C_(min). When such coincidenceoccurs, the comparator 60 simultaneously restores the low speed supplyto the motor 16 and de-energizes the brake 32.

The carriage then continues to travel in the same direction, at lowspeed, in order to be brought against the detected obstacle.

The same occurs when the sensor 46 comes up against a bar 47materializing a singularity and, in the illustrated example, theapproaching presence of a work station P, and also defining by itslength the slowing down duration from V_(max) to V_(min).

It is worth noting that in the two aforementioned cases, a slowing downcycle takes place leading to the determination of the minimum speedV_(min). If the sensor 46 and the finder 53 should stop sending outsignals, whether during or after the slowing down cycle, then thecircuit 45 would restore the maximum speed V_(max) suply.

It is important, in both the mentioned cases of operation, to providemeans for cutting off the supply to the motor 16 and to ensure a stablestop position for the carriage 5.

For the first case, which corresponds to the presence of an obstacle onthe trackway I, such as the presence of another carriage, the carriageis provided with a contact switch 65 placed on the carriage generalsupply circuit. Said contact switch 65 is, preferably, actuated by anarticulated bumper bar 66 carried by the front face 6e, between stopbuffers 67 between which said bar can retract by contact. Once thecontact switch 65 has been released and no information has been issuedby the sensor 46 or the cell 53, the circuit 45 restores the high speedsupply to the motor 16.

For the second case, each work station P of the transfer machine (FIGS.2 and 15) are equipped with stop means 68 consisting of a stop block 69mounted via a spindle 70 on the structure II. The stop block 69 ispermanently projecting with respect to the plane of the surfaces 1 butit can be retracted by a control member 74 such as an electro-magnet.The stop block 69 is provided in order to constitute an abutment withrespect to the structure of the carriage and, in particular, to acrosspiece 72 joining the stiffening members 37. The crosspiece 72carries a contactor 73, operationally coupled to a lever 73a designed tobe actuated by the limit stop 69. Said contactor 73 is placed on thecarriage general supply circuit in series with the switch 65.Preferably, the stop block 69 is operationally coupled to a ramp 74which is elastically retractable in the progressing direction and whichforms a counter-stop designed to rest behind the crosspiece 72 forimmobilizing the carriage.

The supply of the electromagnet is dependent on the performance of theworking cycle of the work station. The end of said cycle controls theretraction of the stop blockp which releases the contactor 73 which inturn restores the high speed supply to the motor 16 when no informationis sent by the sensor 46 or by the cell 53.

FIG. 4 shows that the general supply circuit can also comprise a generalswitch 75 mounted in series with the contact switch 65 and with thecontactor 73.

As indicated in the foregoing, the transfer machine comprises a trackwayI equipped with motor-driven independent carriages which are providedwith travelling environment detection means and with travelling speedservo-control means.

It is then possible to produce a transfer machine comprising a trackwayI with a structural limited to the definition of rolling surfaces 1 andof lateral guiding surfaces 2. Such a trackway can then be a simpleconstruction, with reasonable overall dimensions, in particularthickness-wise, yet offering great adaptability and mountingpossibilities, due to the absence of intermediate or related driving ortransfer members, as is the case with the conventional machines withfree carriages.

And, it is likewise possible to produce a transfer machine with anoutput which is exactly adapted to the operations to be performed at thework stations, and with an automatic adaptability to a possibly varyingoperation process. Indeed, in all cases, each carriage can adapt its owntravelling speed in optimum manner, between leaving the first workstation and, either reaching an obstacle or reaching the next workstation.

Consequently, a transfer machine produced in application of theinvention comprises, a trackway I of the type described hereinabove,means 47 for the remote signalling of the different stations P, stoppingmeans 68 related to each station P as well as electrical rechargingmeans and motor-driven autonomous carriages of which the source of poweris recharged by the cooperation between the blocks 41 and the readcontacts 42. In this way, an adequate reserve of power is alwaysavailable on-board to ensure the travelling autonomy of the carriage,even at maximum speed, between two successive work stations.

In addition to the advantage procured by a simple construction of thetrackway I and by the versatility resulting from the self-adaptabilityof the carriages travelling speed, it is worth noting that, due to theway in which the machine works, it is possible for the sequences ofoperations performed at each work station, to progress with accuracy andreproducibility. Indeed, each carriage is effectively immobilized in astable non-supplied condition, which, on the one hand, saves the powerstored on-board, and on the other hand, does away any driving orfrictional stresses, as is generally the case with the conventionalmachines. In this way, the stop block 69 undergoes no stresses whichcould damage it, whether it has stopped one carriage at one station orseveral carriages which have arrived upstream and are packedhorizontally together against the carriage being attended to. Indeed, insuch a case, all the packed carriages are de-energized by controllingthe contact switches 65 via the bumper bars 66.

In order to enable a carriage to stop with greater exactness in front ofa work station, the transfer machine may also be equipped, in front ofeach work station P, as diagrammatically illustrated in dot-and-dashlines in FIG. 8, with indexing means 76 provided for immobilizing eachcarriage exactly with respect to the operating members of each workstation. The means 76 may comprise a driving member 77 such as a jack,controlling the extension of a pin 78 designed to penetrate into ahousing 79 provided in at least one of the stiffening members 37.

It would also be possible to build a transfer machine comprising atrackway I without the bars 47, and carriages driven at only one lowtravelling speed and without a brake. In such a case, the travellingcontrol would no longer be dependent on a circuit 45, but would beachieved, for all or nothing, by the contact switch 65 and by thecontactor 73. An intermediate version could also consist in adding inthe sensor 46 capable of cooperating with the bars 47.

In the above-referred embodiments, the motorized carriages could beequipped with a free wheel 80 acting as an interposed anti-backingmeans, as illustrated in FIG. 4, between the shaft 12 and a bearing 14.

The fact of using a motorized carriage gives the added possibility ofproducing transfer machines with trackways able to have a positive ornegative gradient. It is indeed possible, as illustrated in FIG. 16, forthe wheels 9 to be covered with teeths 81, either entirely, as shown onthe left of the figure, or only partly, as on the right of the figure.Each tooth 81 can cooperate with a tooth rack 82 formed on the surfaces1 or mounted thereon. The combination of the teeth 81 and of the toothrack 82 also procures to the carriages the best characteristics ofacceleration and deceleration.

FIGS. 17 and 18 show another embodiment according to which the carriageis designed so as to comprise a motorized rear train 10 and a fronttrain 90 constituted by two wheels 91 mounted idle on pins 92 extendingvertically, from the face 6b of the plate 6.

In such a case, the carriage is also provided, on its lower face 6b andclose to the longitudinal edges, with bumping blocks 93 each onepresenting, in the direction of the front face 6e, a V-block 94, ofwhich the base 95, of semi-circular shape, has a center situated on thegeometrical axis of the shaft 12 of the motorized rear train 10.

Each bumping block 93 is designed to cooperate with a pivoting finger 96carried by the trackway I and aligned with the path followed by theblock. Finger 96, which is actuated by a jack 97, comprises acylindrical stud 98 adapted to be engaged in the V-block 94 in order tonest in the base 95 when the carriages is moving at low speed. The stud98 rises from a truncated bearing surface 99 situated, when the finger96 is in extended position, at a level higher than that of the lowerface of the bumping block 93.

As clearly shown in FIGS. 19 and 20, the low speed progression of thecarriage, when a finger 96 is in extended position, causes thecorresponding V-block 94 to fit over the stud 98, whereas,simultaneously, the lower face of the bumping block 93 climbs over thetruncated surface 99. The carriage is thus raised laterally, of a smallamount but sufficient for the corresponding wheel 9 of the motorizedrear train 10, to be raised up with respect to the travelling plane ofsurface 1, whereas the second wheel 9 of the same train, still rests onthe corresponding surface 1. Then, as a result, a pivoting moment isgenerated by the driving action of the outer wheel 9 to the pivotingfinger 96 which constitutes a pivoting center for the whole carriageunder the action of said outer wheel 9. The carriage can pivot freelydue to the presence of the idle wheels 91 constituting the front train,insofar as the trackway I offers them a continuous support andtravelling plane. Thus, by providing, as illustrated in FIG. 21,downstream of a finger 96, a pivoting area 100, it becomes possible toobtain a transfer machine with a trackway comprising rectilinear travelsegments S₁ and pivoting segments S₂ covering an angular value range ofa few degrees and 180°. Indeed, as long as the pivoting finger 96 is inprojecting position, a carriage bumping into it via one of its blocks 93pivots about the stud at low speed under the action of the outer drivingwheel, while being supported by the plane surface of the pivoting area100. When the finger 96 is retracted in, the two wheels 9 of themotorized rear train are returned in contact with the travelling planeand propel the carriage along a rectilinear path in a new direction. Theretraction of finger 96 can, for example, be controlled by a proximitysensor 101 placed on the carriage pivoting path.

FIG. 21 shows that, by successive pivoting movements, it becomespossible to produce a transfer machine which comprises, at intervals orin selected and optionally varying spots, junctions, parallel by-passtracks or any other travelling conformation heretofore unknown in theconventional machines. The implantation of pivoting areas 100 can alsobe instantly and readilyachieved as there are no driving members havingto take into account the displacement of the carriages.

Preferably, each pivoting area is associated, upstream, to a bar 47detected by the sensor 46 in order to trigger, via circuit 45, theslowing down speed recommended for the approach of the stud 96. Thetravelling speed is maintained to a reduced value during the pivotingphase by a signal transmitted to the servo-control circuit by a presencesensor 102 incorporated to the stop blocks. When the stud is retractedat end of pivoting, the bumping signal disappears and the circuit 45restores the maximum speed supply to motor 16.

FIG. 21 also shows that the simple design of the trackway I gives thepossibility of providing a switching module 103, comprising for example,an intermediate rectilinear segment s₁ which can be placed by anactuator 104 either in alignment in a segment S₁ which it contributes todefining, or opposite a by-pass track I_(a). Such a module itselfcomprises a stop block, and the segment S₁ to which it is associated isthen also provided, upstream, with the same stop block. Differentswitching combinations may be considered, using, in each case, only oneguiding and carrying structure and only one two-way actuator.

The operation of a switching or deviation means such as a stud 96 or amodule 103 can be controlled by a passage counter, a code reader placedon the track and detecting the carriages or the loads that theytransport.

A trackway in a machine according to the invention can also comprise asegment pivoting about a horizontal axis, whenever a way has to betemporarily opened through the track.

What is claimed is:
 1. Free transfer machine of the type comprising atrackway (I) set up in relation with work stations (P) and independenttravelling carriages (5) which are carried, guided and driven along thetrackway and which are adapted to the transfer the loads which theysupport, from one work station to another, each carriage being equippedwith a train of driving wheels actuated by an on-board electric drivemember energized from an on-board battery, transfer machine wherein:eachcarriage comprises:a variable speed motor (15), a rechargeable batteryconnected to contact blocks (41), and an individual travelling controlsystem comprising a motor supply and control circuit (45) which iscontrolled by a contact switch (65) actuated by a front bumper bar (66)mounted for pivoting on a front face of each carriage and retractablebetween buffers (67), said bar actuating the contact switch and by acontactor (73) mounted in series with the contact switch and carried bythe lower face of the carriage in such a way as to be actuated byretractable stop members, (6a) provided at each work station to actuatethe contactor (73) so as to cut off the power supply to the motor wheneither the contact switch (65) or the contactor (73) is actuated toprevent the carriage from hitting another carriage and to accuratelyposition the carriage at a work station, said circuit being furthermoreplaced under the control of environment sensors (46,53), the trackway(I) having a generally upwardly opening, "U" shaped cross-sectioncomprising a pair of generally parallel rails (R₁, R₂) defininggenerally horizontal running surfaces and lateral guiding surfaces, thedistance between the lateral guiding surfaces being greater than alateral dimension of the carriage, and reed-contacts (42) located ateach work station connected to an electric charge device and adapted tocooperate with the contact blocks (41) to re-charge the on-board batterywhen the carriage stops at the work station.
 2. Transfer machine asclaimed in claim 1, wherein the environment sensors comprise aninductive sensor (46) carried by each carriage and metallic bars (47)adapted via supports (46) on the trackway upstream of singularitiespresent on said trackway.
 3. Transfer machine as claimed in claims 1wherein the environment sources further comprise, a telemetric presencefinder (53) situated on the front face (6e) of each carriage andconnected in parallel with said inductive sensor (46).
 4. Transfermachine as claimed in claim 1 wherein said machine comprises carriages(5) equipped with an electromagnetic brake (32) associated with thetrain of driving wheels (10) and supplied by the control circuit (45).5. Transfer machine as claimed in claim 4, wherein the electromagneticbrake comprises, on the one hand, an annular magnetic coil (33),connected electrically to the control circuit, which surrounds a drivingshaft proximate to a wheel (9) and presenting in facing relationship toa lateral face of said wheel an annular friction disk (34) and, on theother hand, on a lateral face of said wheel, an annular disk of magneticmaterial mounted via elasticaly deformable strips, said disk beingimmobilized angularly on said wheel but being movable laterally withrespect to the latter under the magnetic action of a coil.